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Deuterium isotopomers as a tool in environmental research
Umeå University, Faculty of Medicine, Medical Biochemistry and Biophsyics.
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes the development and the use of quantitative deuterium Nuclear Magnetic Resonance spectroscopy (NMR) as a tool in two areas of environmental research: the study of long term climate-plant interactions and the source tracking of persistent organic pollutant.

Long-term interactions between plants and climate will influence climate change during this century and beyond, but cannot be studied in manipulative experiments. We propose that long tree rings series can serve as records for tracking such interactions during past centuries.

The abundance of the stable hydrogen isotope deuterium (D) is influenced by physical and biochemical isotope fractionations. Because the overlapping effects of these fractionations are not understood, studies of the D abundance of tree rings led to conflicting results. We hypothesized that both types of fractionations can be separated if the D abundance of individual C-H groups of metabolites can be measured, that is if individual D isotopomers are quantified.

The first paper describes a technique for quantification of D isotopomers in tree-ring cellulose by NMR. The technique showed that the D isotopomers distribution (DID) was non-random. Therefore, the abundance of each isotopomer potentially contains individual information which suggests an explanation for the conflicting results obtained by measuring the overall D abundance (dD).

In the second paper, this technique was used to study hydrogen isotope exchange during cellulose synthesis in tree rings. This revealed that some C-H positions exchange strongly with xylem water, while others do not. This means that the exchanging C-H positions should acquire the D abundance of source water, which is determined by physical fractionations, while non-exchanging C-H positions of tree-ring cellulose should retain biochemical fractionations from the leaf level. Therefore, the abundance of the corresponding D isotopomers should contain information about climate and physiology. When analysing tree-ring series, the DIDs should reflect information about temperature, transpiration and regulation of photosynthesis.

In the third paper, we showed that CO2 concentration during photosynthesis determines a specific abundance ratio of D isotopomers. This dependence was found in metabolites of annual plants, and in tree-ring cellulose. This result shows that D isotopomers of tree-ring series may be used to detect long-term CO2 fertilisation effects. This information is essential to forecast adaptations of plants to increasing CO2 concentrations on time scales of centuries.

In the fourth paper, the source of persistent organic pollutants in the environment was tracked using DID measurements. The dD values of two compounds of related structures were not enough to show indisputably that they did not originate from the same source. However, the DIDs of the common part between the two compounds proved that they did not originate from the same source. These results underline the superior discriminatory power of DIDs, compared to dD measurements.

The versatility of DID measurements makes them a precious tool in addressing questions that can not be answered by dD measurements.

Place, publisher, year, edition, pages
Umeå: Medicinsk kemi och biofysik , 2006. , 45 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1070
Keyword [en]
deuterium, NMR, isotopomers, CO2 response, climate reconstruction, persistent pollutants, stable isotopes
National Category
Environmental Sciences
URN: urn:nbn:se:umu:diva-938ISBN: 91-7264218-1OAI: diva2:145123
Public defence
2006-12-08, KB3A9, Kemi Huset, Umeå University, Umeå, 13:30 (English)
Betson, Tatiana RAvailable from: 2006-11-20 Created: 2006-11-20 Last updated: 2009-09-30Bibliographically approved
List of papers
1. Quantification of deuterium isotopomers of tree-ring cellulose using nuclear magnetic resonance.
Open this publication in new window or tab >>Quantification of deuterium isotopomers of tree-ring cellulose using nuclear magnetic resonance.
2006 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 78, no 24, 8406-8411 p.Article in journal (Refereed) Published
Abstract [en]

Stable isotopes in tree rings are important tools for reconstruction of past climate. Deuterium (D) is of particular interest since it may contain climate signals and report on tree physiology. Measurements of the D/H ratio of tree-ring cellulose have proven difficult to interpret, presumably because the D/H ratio of the whole molecule blends the abundances of the seven D isotopomers of cellulose. Here we present a method to measure the abundance of the D isotopomers of tree-ring cellulose by nuclear magnetic resonance spectroscopy (NMR). The method transforms tree-ring cellulose into a glucose derivative that gives highly resolved, quantifiable deuterium NMR spectra. General guidelines for measurement of D isotopomers by NMR are described. The transformation was optimized for yield and did not alter the original D isotopomer abundances, thus, conserving the original signals recorded in wood cellulose. In the tree-ring samples tested, the abundances of D isotopomers varied by approximately ±10% (2% standard error). This large variability can only be caused by biochemistry processes and shows that more information is present in D isotopomer abundances, compared to the D/H ratio. Therefore, measurements of the D isotopomer distribution of tree rings may be used to obtain information on long-term adaptations to environmental changes and past climate change.

Cellulose/*analysis/chemistry, Climate, Deuterium/*chemistry, Ecosystem, Environmental Monitoring, Glucose/analogs & derivatives/*analysis, Isotope Labeling, Magnetic Resonance Spectroscopy/*methods, Trees/chemistry/*growth & development
urn:nbn:se:umu:diva-6612 (URN)10.1021/ac061050a (DOI)17165833 (PubMedID)
Available from: 2007-12-16 Created: 2007-12-16 Last updated: 2015-03-18Bibliographically approved
2. Hydrogen exchange during cellulose synthesis distinguishes climatic and biochemical isotope fractionations in tree rings.
Open this publication in new window or tab >>Hydrogen exchange during cellulose synthesis distinguishes climatic and biochemical isotope fractionations in tree rings.
2006 (English)In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 172, no 3, 490-499 p.Article in journal (Refereed) Published
Abstract [en]

• The abundance of the hydrogen isotope deuterium (D) in tree rings is an attractive record of climate; however, use of this record has proved difficult so far, presumably because climatic and physiological influences on D abundance are difficult to distinguish.

• Using D labelling, we created a D gradient in trees. Leaf soluble sugars of relatively low D abundance entered cellulose synthesis in stems containing strongly D-labelled water. We used nuclear magnetic resonance (NMR) spectroscopy to quantify D in the C-H groups of leaf glucose and of tree-ring cellulose.

• Ratios of D abundances of individual C-H groups of leaf glucose depended only weakly on leaf D labelling, indicating that the D abundance pattern was determined by physiological influences. The D abundance pattern of tree-ring cellulose revealed C-H groups that exchanged strongly (C(2)-H) or weakly (C(6)-H2) with water during cellulose synthesis.

• We propose that strongly exchanging C-H groups of tree-ring cellulose adopt a climate signal stemming from the D abundance of source water. C-H groups that exchange weakly retain their D abundance established in leaf glucose, which reflects physiological influences. Combining both types of groups may allow simultaneous reconstruction of climate and physiology from tree rings.

Cellulose/*biosynthesis, Climate, Deuterium/metabolism, Hydrogen/chemistry/*metabolism, Picea/*metabolism, Plant Leaves/chemistry, Quercus/*metabolism, Soil/analysis, Water/analysis
urn:nbn:se:umu:diva-6613 (URN)10.1111/j.1469-8137.2006.01843.x (DOI)17083679 (PubMedID)
Available from: 2007-12-16 Created: 2007-12-16 Last updated: 2015-03-18Bibliographically approved
3. Deuterium isotopomers record a CO2 response of plants in leaves and tree rings
Open this publication in new window or tab >>Deuterium isotopomers record a CO2 response of plants in leaves and tree rings
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
urn:nbn:se:umu:diva-2165 (URN)
Available from: 2007-03-15 Created: 2007-03-15 Last updated: 2011-03-30Bibliographically approved
4. Baseline isotopic data of polyhalogenated compounds.
Open this publication in new window or tab >>Baseline isotopic data of polyhalogenated compounds.
Show others...
2006 (English)In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 577, no 2, 250-256 p.Article in journal (Refereed) Published
urn:nbn:se:umu:diva-6540 (URN)10.1016/j.aca.2006.06.054 (DOI)17723680 (PubMedID)
Available from: 2007-12-13 Created: 2007-12-13 Last updated: 2011-03-30Bibliographically approved

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